The Carbon footprint of bicycle Production:
OUR CO2E TARGET IS 3 TONNES. ON AVERAGE WE CURRENTLY PRODUCE 10 TONNES OF CO2 PER PERSON...
We all need to have to stop burning fossil fuels by 2050. We need to drop our CO2 consumption by 60% by 2050.
This is going to require a re-orientation of human values and consumption.
- 3 tonne target limit per year = this is the CO2e allowance per person per year
- 3 metric tonnes as apposed to the imperial ton.
- 1 metric tonne = 1000kg (1,000,000 grams) so the maths is very easy..
- 10 tonnes of CO2 is currently the UK average...
I started this researching the carbon footprint to make a bicycle frame. I am not about to demonize any material here as none of the CO2e figures are above 100kgCO2 and are insignificant compared to manufacturing a car.
The 6 tonnes of CO2e used to make a Citroen C1 would easily make at least 60 high end bicycles.
This also demonstrates that by giving up a car you could purchase multiple bicycles in one year and still live within the 3T Carbon limit.
What is the environmental impact of carbon fibre?
It is very hard to find unbiased research based material data all in one place, however I have done some research and compared other frame materials such as Titanium and 4130 steel. Carbon fibre is manufactured by refining oil to obtain acrylonitrile and then spinning this acrylonitrile and baking the spun yarn. Due to the high baking temperature of 1000C or more, 20 kg of CO2 are emitted to manufacture 1 kg of carbon fibre.
This is the carbon footprint based on a Carbon fibre frame that is 1kg. 60% of a frame is actual carbon and 40% is epoxy resin.
Carbon Fibre = 1.0kg frame
- CO2 EMISSION 26.3 kgCO2
- Water Usage 949 L
These figures are hard to ignore, however how do they actually compare to other frame materials?
Titanium = 1.2Kg frame
- CO2 EMISSION 69.75 kgCO2 (highest)
- Water Usage 1410L
Aluminium = 1.5kg frame
- CO2 EMISSION 18 kgCO2
- Water Usage 2235 L (highest)
Low-alloy 4130 steel = 2.2kg frame
- CO2 EMISSION 9.35 kgCO2
- Water Usage 244 L
Each material has its own dirty little secret, however in a bicycle the percentage is not as selfish as car production:
- Carbon off cut waste can be kept and used to make moulds or chop-strand carbon components.
- Titanium has the worst carbon foot print, however like carbon as a material it has excellent ride properties and does does not corrode.
- Aluminium has very high water useage and the material extraction involves heavy industry and does not have a good life due to material fatigue.
- Steel has a very low carbon foot print, however the other materials that go into Chromoly steel contaminate the environment.
Chromoly Steel is an alloy made from steel, chromium and molybdenum. Like aluminium, Steel production has a number of impacts on the environment, including air emissions (CO, SOx, NOx, PM2), wastewater contaminants, hazardous wastes, and solid wastes.
- Environmental effects of steel: The major environmental impacts from integrated steel mills are from coking and iron-making.
- Environmental effects of chromium: There are several different kinds of chromium that differ in their effects upon organisms.
- Environmental effects of molybdenum: Molybdenum can be highly toxic at large doses. Fodder with more than 10 ppm of molybdenum would put most livestock
Carbon gets a hard time for its headline energy consumption figure involved to produce it. Manufacturing carbon fibre is an energy hungry process, compared to chromloy steel. However it is made in a lab conditions in a controlled environment without the use of ore extraction and the pollution associated with heavy industry. All of the above makes the carbon full life cycle impact look a lot better. However as with any material, if designed thoughtfully it will last a lifetime.
Carbon fibre doesn’t corrode, degrade, rust or fatigue. That means it has a much longer lifecycle, so it potentially only has to be produced once where an aluminium part would have to be replaced multiple times. I am never happy seeing so many cheap frames which end up being disposed of after a few years of use.
So how does this compare on our 3T CO2e Footprint limit? All materials have a CO2E footprint of less than 100kg when building a bicycle frame.
There is room in your 3.0 Tonne CO2e limit to have more than 1 bicycle from any material.